1. Field of the Invention
The present invention relates to an implantable medical apparatus for detecting diastolic heart failure, DHF, of the type having a DHF determining device for determining at least one DHF parameter for detecting a DHF state of the heart of a patient. The invention also relates to a pacemaker having such an apparatus, and a method for detecting diastolic heart failure, DHF, including the step of determining at least one DHF parameter for detecting a DHF state.
2. Description of the Prior Art
There is a growing recognition that congestive heart failure caused by a predominant abnormality in the diastolic function, i.e. diastolic heart failure, DHF, is both common and causes significant morbidity and mortality. Therefore early detection of DHF is important such that a suitable treatment can be started. Patients do not, however, seem to have symptoms at an early stage. In addition it has been hard to separate diastolic and systolic heart failure and they may also exist simultaneously.
The time progress of different phases of diastole of a patient suffering from DHF is changed vis-à-vis that of a healthy person, see Michael R. Zile and Dirk L. Brusaert, “New Concepts in Diastolic Dysfunction and Diastolic Heart Failure: Part I”, Circulation 2002; 105: 1387. Thus DHF can be divided into three phases, see FIG. 1. FIG. 1a shows left atrial pressure, LA dotted line, and left ventricular pressure, LV solid line, as functions of time for a normal, healthy state and for three phases of DHF. The first phase of DHF is referred to as “Impaired Relaxation”. In this phase characteristic times related to relaxation and filling of the left ventricle is prolonged compared to corresponding times of a normal heart. After this phase the disease progresses into a phase called “Pseudonormal”. In this phase the heart compensates and the characteristic times returns to more normal values, close to those of the normal heart. This phase is followed by the final phase of DHF called “Restrictive”. In the final phase the characteristic times are shorter than for the normal heart. FIG. 1b shows corresponding measured mitral blood flow velocities. Letter “E” denotes the so-called E-wave, early filling of the ventricle, and “A” the A-wave, contribution from the atrium during its contraction.